The present invention generally relates to a golf club head, an iron golf club head, a wood golf club head, and a golf club set. Specifically, it relates to a golf club head, an iron golf club head, a wood golf club head that can improve the directivity of a flying ball and increase the flying distance by restraining the rotation of the golf club head in striking a golf ball with the golf club head, and a golf club set using the golf club heads.
The first conventional example of a golf club head is described in Japanese Patent Application Laid-open No. 07-67991(1995). In this document, the toe weight and the hosel weight have a center of mass positioned above the horizontal line that passes through the center of gravity of the golf club head when the gold club head is in an addressed position.
Further, the second conventional example is described in Japanese Patent Application Laid-open No. 09-149954(1997). In this document, X-axis, Y-axis, and Z-axis that intersect perpendicularly to each other are set using the center of gravity of the gold club head as an origin. The angle formed by X-axis and the line obtained by projecting onto XZ-plane the principal axis of inertia having the smallest angle with X-axis among the three principal axes of inertia of the golf club head that intersect perpendicularly to each other, is not smaller than 10xc2x0 and not larger than 40xc2x0.
Further, a wood golf club as the third conventional example is described in Japanese Patent Application Laid-open No. 01-300970(1989). This document discloses a technique of providing a horizontal principal axis of inertia by setting the weight of the hosel part to be not larger than 5% of the weight of the golf club head body and setting the length of the hosel part to be not larger than 4 cm.
Further, as a technique for improving the directivity of a hit ball, a technique of increasing the moment of inertia of a golf club head is known. As the fourth conventional example, a so-called cavity structure is known in which a cavity part is provided in the inside of an iron golf club head body and the peripheral part is made thick to increase the moment of inertia. Also, as the fifth conventional example, a hollow structure is known in which the inside of an iron golf club head is made into a complete cavity.
The flying distance and the directivity of a hit ball may be mentioned as the characteristics required in a golf club. Particularly, the directivity is a great factor that is related to fairway keep and green keep, and gives an influence on the score. The directivity is determined by the position (hitting point position) at which the golf club head is brought into contact with a golf ball. Apart from professional golfers and top amateurs, most of the general players strike the golf ball at various locations on the upper side, the lower side, the right side, and the left side of the face surface of the golf club head. For this reason, the directivity of the hit ball decreases if the golf ball impinges on the position out of the center of gravity, although the directivity of the hit ball is good if the golf ball impinges on a neighborhood of the center of gravity of the golf club head.
Thus, in order to prevent decrease in the directivity even if the golf ball impinges on a position located away from the center of gravity of the golf club head, a method of increasing the moment of inertia of the golf club head, particularly the moment of inertia in the direction from the toe part to the heel part of the golf club when the golf club head is placed on a plane, is proposed.
The first conventional example does not disclose a technique of restraining the rotation of the golf club head at the time of striking. The second conventional example does not disclose a technique of restraining the rotation of the golf club head at the time of striking, either.
Also, the distribution shape of the variation of the points at which: the golf ball impinges on the face surface has a width in the up-and-down direction of the face surface. Further, the shape of the variation changes depending on the golf clubs having different identification numbers. For this reason, it is necessary not only to improve the directivity of the hit ball in the right-and-left direction but also to reduce the variation of the flying distance.
Furthermore, the aforesaid third example involves a problem that the variation of the flying distance of the hit ball cannot be reduced.
Further, even the aforesaid fourth and fifth conventional examples fail to disclose a technique of restraining the rotation of the golf club head.
Therefore, the object of the present invention is to provide a golf club head and a golf club set that can reduce the variation of the hit ball in the right-and-left direction and the variation of the flying distance.
A golf club head according to one aspect of the present invention has an ellipsoid of inertia with its center at the center of gravity. When the ellipsoid of inertia is virtually cut with a plane passing through the center of gravity of the golf club head and being parallel to a face surface, the major axis of a plane ellipse appearing on its cut surface forms an angle of xcex8 with an intersecting line of the cut surface and the ground surface. The major axis extends upward and away from the ground surface as it approaches a toe part. The angle xcex8 is not smaller than 0.5xc2x0 and not larger than 9.5xc2x0. An aspect ratio a/b defined by a ratio of the length a of the major axis to the length b of the minor axis is not smaller than 1 and not larger than 4.
A golf club set according to one aspect of the present invention includes a plurality of golf clubs having different identification numbers. Each of the plurality of golf clubs has a golf club head and a shaft connected to the golf club head. Each of the golf club heads has an ellipsoid of inertia with its center at the center of gravity. When the ellipsoid of inertia is virtually cut with a plane passing through the center of gravity of the golf club head and being parallel to a face surface, the major axis of a plane ellipse appearing on its cut surface forms an angle of xcex8 with an intersecting line of the cut surface and the ground surface. The major axis extends upward and away from the ground surface as it approaches a toe part. The angle xcex8 is not smaller than 0.5xc2x0 and not larger than 9.5xc2x0. An aspect ratio a/b defined by a ratio of the length a of the major axis to the length b of the minor axis is not smaller than 1 and not larger than 4. The angle xcex8 of each of the plurality of golf club heads increases successively or remains approximately equal according as the identification number increases. The aspect ratio a/b of each of the plurality of golf club heads decreases successively or remains approximately equal according as the identification number increases.
Preferably, the angle xcex8 increases successively with an approximately constant ratio according as the identification number of the golf club head increases.
Also, preferably, the aspect ratio a/b decreases successively with an approximately constant ratio according as the identification number of the golf club head increases.
A golf club head according to another aspect of the present invention has an ellipsoid of inertia with its center at the center of gravity. When the ellipsoid of inertia is virtually cut with a plane passing through the center of gravity of the golf club head and being parallel to a face surface, the major axis of a plane ellipse appearing on its cut surface forms an angle of xcex8 with an intersecting line of the cut surface and the ground surface. The major axis extends upward and away from the ground surface as it approaches a toe part. The angle xcex8 is not smaller than 0.50 and not larger than 9.5xc2x0. The height h of a sweet spot from the ground surface is not smaller than 10 mm and not larger than 30 mm.
A golf club set according to another aspect of the present invention includes a plurality of golf clubs having different identification numbers. Each of the plurality of golf clubs has a golf club head and a shaft connected to the golf club head. Each of the golf club heads has an ellipsoid of inertia with its center at the center of gravity. When the ellipsoid of inertia is virtually cut with a plane passing through the center of gravity of the golf club head and being parallel to a face surface, the major axis of a plane ellipse appearing on its cut surface forms an angle of xcex8 with an intersecting line of the cut surface and the ground surface. The major axis extends upward and away from the ground surface as it approaches a toe part. The angle xcex8 is not smaller than 0.5xc2x0 and not larger than 9.5xc2x0. The angle xcex8 of each of the plurality of golf club heads increases successively or remains approximately equal according as the identification number increases. The height h of the sweet spot of each of the plurality of golf club heads decreases successively or remains approximately equal according as the identification number increases.
Also, preferably, the angle xcex8 increases successively with an approximately constant ratio according as the identification number of the golf club increases.
Also, preferably, the height h of the sweet spot decreases successively with an approximately constant ratio according as the identification number of the golf club increases.
A golf club head according to still another aspect of the present invention has an ellipsoid of inertia with its center at the center of gravity. When the ellipsoid of inertia is virtually cut with a plane passing through the center of gravity of the golf club head and being parallel to a face surface, an aspect ratio a/b defined by a ratio of the length a of the major axis to the length b of the minor axis of a plane ellipse appearing on its cut surface is not smaller than 1 and not larger than 4. The height h of a sweet spot from the ground surface is not smaller than 10 mm and not larger than 30 mm.
Also, preferably, the major axis forms an angle of xcex8 with an intersecting line of the cut surface and the ground surface. The major axis extends upward and away from the ground surface as it approaches a toe part. The angle xcex8 is not smaller than 0.5xc2x0 and not larger than 9.5xc2x0.
A golf club set according to still another aspect of the present invention includes a plurality of golf clubs having different identification numbers. Each of the plurality of golf clubs has a golf club head and a shaft connected to the golf club head. Each of the golf club heads has an ellipsoid of inertia with its center at the center of gravity. When the ellipsoid of inertia is virtually cut with a plane passing through the center of gravity of the golf club head and being parallel to a face surface, an aspect ratio a/b defined by a ratio of the length a of the major axis to the length b of the minor axis of a plane ellipse appearing on its cut surface is not smaller than 1 and not larger than 4. The height h of a sweet spot from the ground surface is not smaller than 10 mm and not larger than 30 mm. The aspect ratio a/b of each of the plurality of golf club heads decreases successively or remains approximately equal according as the identification number increases. The height h of the sweet spot of each of the plurality of golf club heads decreases successively or remains approximately equal according as the identification number increases.
Also, preferably, the major axis forms an angle of xcex8with an intersecting line of the cut surface and the ground surface. The major axis extends upward and away from the ground surface as it approaches a toe part. The angle xcex8 is not smaller than 0.5xc2x0 and not larger than 9.5xc2x0. The angle xcex8 of each of the plurality of golf club heads increases successively or remains approximately equal according as the identification number increases.
Also, preferably, the aspect ratio a/b decreases successively with an approximately constant ratio according as the identification number of the golf club increases.
Also, preferably, the height h of the sweet spot decreases successively with an approximately constant ratio according as the identification number of the golf club increases.
Also, preferably, the angle xcex8 increases successively with an approximately constant ratio according as the identification number of the golf club increases.
An iron golf club head according to the present invention includes a head body having a toe, a sole, and a heel; a first weight member disposed in an upper part of the toe of the head body; and a second weight member disposed in a heel side part of the sole of the head body.
Preferably, the first weight member has a larger specific gravity than a material constituting the head body.
Preferably, the second weight member has a larger specific gravity than a material constituting the head body.
Preferably, the first weight member has a larger density than other parts of the head body.
Preferably, the second weight member has a larger density than other parts of the head body.
Preferably, the head body has a back cavity.
Preferably, the depth of the back cavity increases according as it approaches from a lower part of the toe to a heel part.
Preferably, the width of a sole part decreases according as it approaches from a lower part of the toe to a heel part.
Preferably, the head body has a through-hole, and further includes an insert member fitted into the through-hole so as to form a back cavity.
A wood golf club head according to the present invention includes a head body having a toe, a sole, and a back; a first weight member disposed in an upper part of the toe of the head body; and a second weight member disposed in a back part of the center of the sole of the head body.
Preferably, the first weight member has a larger specific gravity than a material constituting the head body.
Preferably, the second weight member has a larger specific gravity than a material constituting the head body.
Preferably, the first weight member includes a part having a larger thickness than other parts of the head body.
Preferably, the second weight member includes a part having a larger thickness than other parts of the head body.
Preferably, the first weight member has a larger density than other parts of the head body.
Preferably, the second weight member has a larger density than other parts of the head body.
Preferably, the first weight member includes a part having a larger specific gravity than a material constituting the head body, and a part having a larger thickness than other parts of the head body.
Preferably, the second weight member includes a part having a larger specific gravity than a material constituting the head body, and a part having a larger thickness than other parts of the head body.
Preferably, the first and second weight members have a larger specific gravity than a material constituting the head body.